job-info: support reading/watching updated jobspec

Problem: It is inconvenient that lookup w/ the CURRENT flag and
update-watch support reading/watching a current/updated R but not
a current/updated jobspec.

Support returning a current/updated jobspec.

Author: chu11

src/common/libjob/job.h

@@ -37,7 +37,7 @@ enum job_lookup_flags {
     FLUX_JOB_LOOKUP_JSON_DECODE = 1,
     /* get current value of special fields by applying eventlog
      * updates for those fields
-     * - currently works for R
+     * - currently works for jobspec and R
      */
     FLUX_JOB_LOOKUP_CURRENT = 2,
 };

src/modules/job-info/lookup.c

@@ -173,6 +173,8 @@ static int lookup_current (struct lookup_ctx *l,
 
     if (streq (key, "R"))
         update_event_name = "resource-update";
+    else if (streq (key, "jobspec"))
+        update_event_name = "jobspec-update";
 
     if (!(value_object = json_loads (value, 0, NULL))) {
         errno = EINVAL;
@@ -205,6 +207,12 @@ static int lookup_current (struct lookup_ctx *l,
         if (streq (name, update_event_name)) {
             if (streq (key, "R"))
                 apply_updates_R (l->ctx->h, l->id, key, value_object, context);
+            else if (streq (key, "jobspec"))
+                apply_updates_jobspec (l->ctx->h,
+                                       l->id,
+                                       key,
+                                       value_object,
+                                       context);
         }
     }
 
@@ -288,7 +296,8 @@ static void info_lookup_continuation (flux_future_t *fall, void *arg)
         }
 
         if ((l->flags & FLUX_JOB_LOOKUP_CURRENT)
-            && streq (keystr, "R")) {
+            && (streq (keystr, "R")
+                || streq (keystr, "jobspec"))) {
             if (lookup_current (l, fall, keystr, s, &current_value) < 0)
                 goto error;
             s = current_value;
@@ -442,7 +451,7 @@ static int lookup_cached (struct lookup_ctx *l)
 
     key_str = json_string_value (key);
 
-    if (!streq (key_str, "R"))
+    if (!streq (key_str, "R") && !streq (key_str, "jobspec"))
         return 0;
 
     if ((ret = update_watch_get_cached (l->ctx,

src/modules/job-info/update.c

@@ -83,6 +83,8 @@ static struct update_ctx *update_ctx_create (struct info_ctx *ctx,
         goto error;
     if (streq (key, "R"))
         uc->update_name = "resource-update";
+    else if (streq (key, "jobspec"))
+        uc->update_name = "jobspec-update";
     else {
         errno = EINVAL;
         goto error;
@@ -180,6 +182,12 @@ static void eventlog_continuation (flux_future_t *f, void *arg)
                                  uc->key,
                                  uc->update_object,
                                  context);
+            else if (streq (uc->key, "jobspec"))
+                apply_updates_jobspec (uc->ctx->h,
+                                       uc->id,
+                                       uc->key,
+                                       uc->update_object,
+                                       context);
 
             msg = flux_msglist_first (uc->msglist);
             while (msg) {
@@ -315,6 +323,12 @@ static void lookup_continuation (flux_future_t *f, void *arg)
                                  uc->key,
                                  uc->update_object,
                                  context);
+            else if (streq (uc->key, "jobspec"))
+                apply_updates_jobspec (uc->ctx->h,
+                                       uc->id,
+                                       uc->key,
+                                       uc->update_object,
+                                       context);
             uc->initial_update_count++;
         }
         else if (streq (name, "clean"))
@@ -474,7 +488,7 @@ void update_watch_cb (flux_t *h, flux_msg_handler_t *mh,
         errmsg = "update-watch request rejected without streaming RPC flag";
         goto error;
     }
-    if (!streq (key, "R")) {
+    if (!streq (key, "R") && !streq (key, "jobspec")) {
         errno = EINVAL;
         errmsg = "update-watch unsupported key specified";
         goto error;

src/modules/job-info/util.c

@@ -125,6 +125,25 @@ void apply_updates_R (flux_t *h,
     }
 }
 
+void apply_updates_jobspec (flux_t *h,
+                            flux_jobid_t id,
+                            const char *key,
+                            json_t *jobspec,
+                            json_t *context)
+{
+    const char *ckey;
+    json_t *value;
+
+    json_object_foreach (context, ckey, value) {
+        if (jpath_set (jobspec,
+                       ckey,
+                       value) < 0)
+            flux_log (h, LOG_INFO,
+                      "%s: failed to update job %s %s",
+                      __FUNCTION__, idf58 (id), key);
+    }
+}
+
 /*
  * vi:tabstop=4 shiftwidth=4 expandtab
  */

src/modules/job-info/util.h

@@ -42,6 +42,13 @@ void apply_updates_R (flux_t *h,
                       json_t *R,
                       json_t *context);
 
+/* apply context updates to the jobspec object */
+void apply_updates_jobspec (flux_t *h,
+                            flux_jobid_t id,
+                            const char *key,
+                            json_t *jobspec,
+                            json_t *context);
+
 #endif /* ! _FLUX_JOB_INFO_UTIL_H */
 
 /*